Reactions of Alkenes

One of the most powerful of alkene transformations is enantioselective
epoxidation. Tsutomu Katsuki of Kyushu University has developed (Angew. Chem.
Int. Ed.2007, 46, 4559.
)
a Ti catalyst that with H2O2, selectively epoxidized
terminal alkenes with high ee. The same catalyst converted a Z 2-alkene such as
3 into the epoxide. This is significant, because such epoxides are opened with
nucleophiles selectively at the less congested center.

Novel procedures for alkene functionalization have been put forward. Philippe
Renaud of the University of Berne has developed (Adv. Synth. Catal.2008,
350,
1163.
)
a simple protocol for terminal halogenation, based on catalyzed addition
of catecholborane, followed by free radical substitution. Sulfides and selenides
were also prepared. H. Zoghlami of the Faculty of Sciences of Tunis has devised
(Tetrahedron Lett.2007, 48, 5645.
)
an oxidative sulfinylation, converting a
terminal alkene 7 to the sulfide 8. M. Christina White of the University of
Illinois (J. Am. Chem. Soc.2008, 130, 3316.
)
and Guosheng Liu of the Shanghai
Institute of Organic Chemistry (Angew. Chem. Int. Ed.2008, 47, 4733.
)
independently developed Pd catalysts for the oxidation of a terminal alkene
9 to the terminal allylic amine 10. Shannon S. Stahl of the University of
Wisconsin-Madison has established (Org. Lett.2007, 9, 4331.
)
conditions for
the complementary transformation of a terminal alkene 11 to the enamide
12.
Douglas B. Grotjahn of San Diego State University has optimized (J. Am. Chem. Soc.2007, 129, 9592.
)
Ru-catalyzed alkene (“zipper”) migration, effecting the
conversion of 13 to 14 and of 15 to 16.

There have been several new observations on alkene cleavage. Marcus A. Tius
of the University of Hawaii and Bakthan Singaram of the University of California,
Santa Cruz have found (Tetrahedron Lett.2008, 49, 2764.
)
that epoxides such as
17 are cleaved directly by NaIO4, providing a simple alternative to ozonolysis.
Rolando A. Spanevello of the Universidad Nacional de Rosario has extended (Tetrahedron2007, 63, 11410.
)
unsymmetrical ozonolysis to highly substituted norbornene
derivatives such as 19, observing 20 as the only product. Patrick H. Dussault of
the University of Nebraska-Lincoln has established (J. Org. Chem.2008,
73,
4688.
)
that alkene ozonolysis in wet acetone delivered the ketone or aldehyde
directly, without reductive workup.

In a very simple procedure, Takashi Kamitanaka and Tadao Harada of Ryukoku
University and the Industrial Research Center of Shiga Prefecture have found (Tetrahedron
Lett. 2008, 48, 8460.
)
that acetone, acetonitrile or an alcohol added without
catalyst to a terminal alkene at 340°C. Yoshiji Takemoto of Kyoto University
has reported (J. Org. Chem.2007, 72, 5898.
)
Pd-catalyzed acylation of 9-BBN
adducts, and Michael G. Organ of York University has described (Chem. Commun.2008, 735.
)
a convenient Pd catalyst for coupling of 9-BBN adducts with primary
alkyl bromides at ambient temperature. Dieter Vogt of the Eindhoven University
of Technology (Adv. Synth. Catal.2008, 350, 332.
)
and Maurizio Taddei of the
Universitā degli Studi di Siena (Tetrahedron Lett.2008, 48, 8501.
)
have reported
hydroformylation in the presence of a secondary amine to give net
aminomethylation, and Bernhard Breit of the Albert-Ludwigs-Universität Freiburg
has found (Adv. Synth. Catal.2008, 350, 989.
)
that hydroformylation can be
followed by Knoevenagel condensation, to give three-carbon homologation, to 28.
Melanie S. Sanford of the University of Michigan has devised (J. Am. Chem. Soc.2008, 130, 2150.
)
strategies for interrupting Heck arylation, to give selectively
either 29 or 30, and Andrew J. Phillips of the University of Colorado has taken
advantage of Kulinkovich cyclopropanation to give selectively either 31 or
32 (Org.
Lett.2007, 9, 2717,
); 2008,
10, 1083.
).